There can be two possibilities.
Firstly, your wife gestational age
might be lesser than what has been calculated that is she might not be 7 weeks in term of growth of the baby.
In such a case you should not be worried. As your doctor has called for a repeat ultrasound
, its possible that the heart rate
is visualized this time.
The other possibility can be that you have a non viable fetus where in abortion
occurs. But before coming to this conclusion, I would suggest you to follow your doctor's advice and get the repeat scan done.